In the related art, generally, as a technique for exploring and analyzing underground geophysical properties, a radar exploring technique which transmits and receives an electromagnetic wave to explore the underground geophysical properties and an electromagnetic (EM) induction exploring technique which explores the underground geophysical properties using a magnetic field have been widely used.
More specifically, the radar exploring technique is a method to explore the underground geophysical properties by transmitting and receiving an electric field signal of approximately 100 MHz to 1 GHz. The electromagnetic induction technique is a method to explore the underground geophysical properties by transmitting and receiving a magnetic field signal of several kHz or lower.
Further, recently, a so-called GPR technique which uses an underground exploring radar or a ground penetrating radar (GPR) to explore the underground geophysical properties by transmitting and receiving an electric field signal is being widely used.
Here, as an example of the related art of the apparatus and method for exploring the underground using the GPR as described above, for example, Korean Registered Patent Publication No. 10-1267017 suggests an underground facility survey system by signal processing of GPR exploration apparatus which is configured to be mounted on a cart to improve mobility so that fatigue of an operator is reduced and configured to attach antennae below the cart at the front side and the rear side to be close to the ground surface thereby minimizing the transmission and reception signal loss and suppressing the electromagnetic wave from being dissipated in the air.
Further, as another example of the related art of the apparatus and method for exploring the underground using the GPR as described above, for example, Korean Registered Patent Publication No. 10-1267016 suggests a signal interpreting apparatus of an underground facility survey by using a GPR system which is configured to more accurately survey using a ultra broadband pulse and easily move an interface for every module, survey in the scene, and move the equipment, and enable a survey speed of 4 km/day, so as to improve a working efficiency through compact integration and considerably reduce the cost.
Furthermore, as still another example of the related art of the apparatus and method for exploring the underground using the GPR as described above, for example, Korean Registered Patent Publication No. 10-1241313 suggests a system and a method using underground exploration radar for diagnosing the safety of a paved road, capable of simultaneously sensing an underground cavity existing under the paved road and the thickness of the paved road at a high speeds, the system including a low frequency radar module which generates and radiates a low frequency band pulse signal and obtains a response signal reflected from a underground cavity formed below a paved road, a plurality of high frequency radar modules which generates and radiates a high frequency band pulse signal and obtains a response signal reflected from a recognizer configured by a metal wire mesh between an intermediate layer and a base layer and between the base layer and a soil layer of the paved road, and an image processing device which displays a signal obtained from the low frequency radar module and the high frequency radar module.
Furthermore, as still another example of the related art of the apparatus and method for exploring the underground using the GPR as described above, for example, Korean Registered Patent Publication No. 10-0365141 suggests detection techniques for the survey of buried structures using a GPR system which is configured to include radiating a pulse generated in a control device through a transmission and reception antenna and receiving a signal reflected from a buried object after passing through a medium, recording and storing a signal transmitted from the reception antenna to transmit data to a CPU required for data processing in the room, determining various variables required to survey such as an initial time when the signal is recorded in the control device, a digital sampling interval of a reception signal which is an analog signal, an entire time range when the signal is recorded, and the number of stacking, generating and amplifying a transmission and reception pulse suitable for the determined variable and then radiating the transmission and reception pulse through the transmission antenna, determining a sampling interval and a sampling interval and the number of sampling per trace, implementing pulse data obtained in the control device as an image and applying various implementation colors to a high resolution screen for the processed data to represent a cross-section with a high resolving power.
As described above, even though various techniques for the devices and methods for exploring the underground using a GPR of the related art have been suggested, the devices and methods for exploring the underground using a GPR of the related art have the following problems.
That is, according to a structure in which a sensor radiates, such as a GPR, since an dipole antenna which is a radiator with a small and simple structure and has a less difference in radiation patterns according to the change of frequency is more useful than a loop type antenna, in the related art, generally, a dipole sensor is mainly used for the GPR to transmit and receive an electric field signal.
In contrast, for the electromagnetic (EM) induction which uses a lower frequency band than that of the GPR, in the electromagnetic induction range, a sensor is very small as compared with the wavelength so that the loop type is relatively more advantageous to adjust the impedance than the dipole type. Therefore, a loop and coil type sensor is mainly used as a sensor which transmits and receives a magnetic field signal.
That is, in the GPR techniques of the related art, as described above, because of the characteristics, it is advantageous to use the dipole sensor, so that only an underground image using an electric field reflected wave is mainly acquired and acquisition of an underground image using a magnetic field reflected wave is relatively excluded.
Therefore, in order to accurately and effectively explore and investigate underground geophysical properties, it is desirably to obtain both an underground image by an electric field signal and an underground image by a magnetic field signal to comprehensively analyze the signals.
Accordingly, as described above, in order to resolve the problems of the GPR exploring techniques of the related art which use only the electric field signal, but exclude the magnetic field signal, it is desirable to provide a underground geophysical property exploring system and method with a new configuration which is configured to obtain not only a underground image using the electric field reflected wave but also an underground image using a magnetic field reflected wave by operating both the electric field signal reception sensor and the magnetic field signal reception sensor. However, a device or a method which satisfies the above-mentioned requirements has not yet been provided.